1. Field of the Invention
The present invention relates to a digital broadcast receiver and, in particular, to a fast channel switching method and apparatus for a digital broadcast receiver that can reduce a channel switching delay caused by limitations in real time broadcasting systems.
2. Description of the Related Art
A digital broadcast receiver is an apparatus that restores original digital data from a broadcast signal transmitted by a broadcasting station. The digital data is coded and modulated so as to be broadcast in the form of a broadcast signal by the broadcasting station. The digital broadcast receiver demodulates and decodes the broadcast signal for restoring the original digital data. The digital broadcast receiver is provided with a tuner, a demodulator, and a decoder.
Digital broadcast systems are classified into a digital multimedia broadcast (DMB) system and a digital video broadcasting (DVB) system. These digital broadcast systems provide a plurality of service channels in a frequency band, and each service channel is structured with multiplexed sub-channels of video, audio, and program information data.
The digital broadcast receiver scans the service channels such that a subscriber can select one of the scanned service channels and switch to another service channel at will.
In digital broadcasting, however, the digital data is highly compressed and thus it takes a considerable amount of time for a screen to become stable after switching service channels, unlike in analog broadcasting. In the case of DVB, data burst repeats for a period of 1 to 4 seconds and thus the screen shows nothing before the data burst is completely buffered after switching the service channels. This switching delay is inconvenient to subscribers.
In the case of DVB-handheld (DVB-H), there are at least 4 basic channels: main channel, electronic service guide (ESG) channel, entitlement management message (EMM) channel, and picture in picture (PIP) channel. In order to reduce the channel switching delay, a DVB-H receiver buffers signals transmitted through the channels adjacent to the main channel. In order to enable buffering of the signals on the adjacent channels, a total of 12 Megabytes (2 Megabytes per channel) are required. However, since the ESG is not always received, the memory capacity for the ESG is wasted.